In this proposal, studies will be continued on the mouse MHC class II la antigens and a new program to study human class II genes will be initiated. In the mouse system, transgenic mice will be generated with exon shuffled la genes from the A(K,A), A(Q,A) and E(K,A) genes to determine the site on the la molecule which presents Mls antigen and super antigens to the T cells. The precise site on the la molecule will be further narrowed down by generating la mutant genes by site directed mutagenesis and producing transgenic mice with them. Regulation of A/alpha and E/beta genes will be determined by constructing la genes with different promotor regions and generating transgenic mice to examine the tissue expression. The importance of the N-linked oligosaccharides in the function of la molecules will be determined by mutating the oligosaccharide attachment sites on the la genes and producing transgenic mice with them. The recombination hot spot which has been identified in the E alpha gene will be determine by DNA sequencing. These studies in the mouse system will increase our understanding of the structure/function relationship of la genes. Using the transgenic technology, mice expressing human class II genes will be generated for further serological characterization and definition of determinants, specificities and epitopes on the human class II molecules and localization to specific chains and domains. These transgenic mice would also be utilized to study the regulation of human la genes. Studies will be initiated using anti- sense RNA to determine the feasibility of downregulating endogenous class II genes in vivo. Finally, structure/function of human class II genes will be studied using the transgenic mice. Since the class II genes play such a crucial role in immune response, self versus non-self regulation, susceptibility to disease and cancer, the information we gain from the mouse and human la genes and their products are critical to understanding the immune system and devising methods of disease prevention and immune therapy. Eventually transgenic mice will be produced expressing human cell II genes and human CD4 gene which will be used to generate a model for AIDS. The lab will continue to serve as a resource for mouse strains, embryo freezing and transgenic technology.